Java tutorial
/* * Licensed to the Apache Software Foundation (ASF) under one or more * contributor license agreements. See the NOTICE file distributed with * this work for additional information regarding copyright ownership. * The ASF licenses this file to You under the Apache License, Version 2.0 * (the "License"); you may not use this file except in compliance with * the License. You may obtain a copy of the License at * * http://www.apache.org/licenses/LICENSE-2.0 * * Unless required by applicable law or agreed to in writing, software * distributed under the License is distributed on an "AS IS" BASIS, * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. * See the License for the specific language governing permissions and * limitations under the License. */ package org.apache.commons.lang.exception; import java.io.PrintStream; import java.io.PrintWriter; /** * The base class of all exceptions which can contain other exceptions. * * It is intended to ease the debugging by carrying on the information * about the exception which was caught and provoked throwing the * current exception. Catching and rethrowing may occur multiple * times, and provided that all exceptions except the first one * are descendants of <code>NestedException</code>, when the * exception is finally printed out using any of the <code> * printStackTrace()</code> methods, the stack trace will contain * the information about all exceptions thrown and caught on * the way. * <p> Running the following program * <p><blockquote><pre> * 1 import org.apache.commons.lang.exception.NestableException; * 2 * 3 public class Test { * 4 public static void main( String[] args ) { * 5 try { * 6 a(); * 7 } catch(Exception e) { * 8 e.printStackTrace(); * 9 } * 10 } * 11 * 12 public static void a() throws Exception { * 13 try { * 14 b(); * 15 } catch(Exception e) { * 16 throw new NestableException("foo", e); * 17 } * 18 } * 19 * 20 public static void b() throws Exception { * 21 try { * 22 c(); * 23 } catch(Exception e) { * 24 throw new NestableException("bar", e); * 25 } * 26 } * 27 * 28 public static void c() throws Exception { * 29 throw new Exception("baz"); * 30 } * 31 } * </pre></blockquote> * <p>Yields the following stack trace: * <p><blockquote><pre> * org.apache.commons.lang.exception.NestableException: foo * at Test.a(Test.java:16) * at Test.main(Test.java:6) * Caused by: org.apache.commons.lang.exception.NestableException: bar * at Test.b(Test.java:24) * at Test.a(Test.java:14) * ... 1 more * Caused by: java.lang.Exception: baz * at Test.c(Test.java:29) * at Test.b(Test.java:22) * ... 2 more * </pre></blockquote><br> * * @author <a href="mailto:Rafal.Krzewski@e-point.pl">Rafal Krzewski</a> * @author <a href="mailto:dlr@collab.net">Daniel Rall</a> * @author <a href="mailto:knielsen@apache.org">Kasper Nielsen</a> * @author <a href="mailto:steven@caswell.name">Steven Caswell</a> * @since 1.0 * @version $Id: NestableException.java 491651 2007-01-01 22:01:32Z ggregory $ */ public class NestableException extends Exception implements Nestable { /** * Required for serialization support. * * @see java.io.Serializable */ private static final long serialVersionUID = 1L; /** * The helper instance which contains much of the code which we * delegate to. */ protected NestableDelegate delegate = new NestableDelegate(this); /** * Holds the reference to the exception or error that caused * this exception to be thrown. */ private Throwable cause = null; /** * Constructs a new <code>NestableException</code> without specified * detail message. */ public NestableException() { super(); } /** * Constructs a new <code>NestableException</code> with specified * detail message. * * @param msg The error message. */ public NestableException(String msg) { super(msg); } /** * Constructs a new <code>NestableException</code> with specified * nested <code>Throwable</code>. * * @param cause the exception or error that caused this exception to be * thrown */ public NestableException(Throwable cause) { super(); this.cause = cause; } /** * Constructs a new <code>NestableException</code> with specified * detail message and nested <code>Throwable</code>. * * @param msg the error message * @param cause the exception or error that caused this exception to be * thrown */ public NestableException(String msg, Throwable cause) { super(msg); this.cause = cause; } /** * {@inheritDoc} */ public Throwable getCause() { return cause; } /** * Returns the detail message string of this throwable. If it was * created with a null message, returns the following: * (cause==null ? null : cause.toString()). * * @return String message string of the throwable */ public String getMessage() { if (super.getMessage() != null) { return super.getMessage(); } else if (cause != null) { return cause.toString(); } else { return null; } } /** * {@inheritDoc} */ public String getMessage(int index) { if (index == 0) { return super.getMessage(); } return delegate.getMessage(index); } /** * {@inheritDoc} */ public String[] getMessages() { return delegate.getMessages(); } /** * {@inheritDoc} */ public Throwable getThrowable(int index) { return delegate.getThrowable(index); } /** * {@inheritDoc} */ public int getThrowableCount() { return delegate.getThrowableCount(); } /** * {@inheritDoc} */ public Throwable[] getThrowables() { return delegate.getThrowables(); } /** * {@inheritDoc} */ public int indexOfThrowable(Class type) { return delegate.indexOfThrowable(type, 0); } /** * {@inheritDoc} */ public int indexOfThrowable(Class type, int fromIndex) { return delegate.indexOfThrowable(type, fromIndex); } /** * {@inheritDoc} */ public void printStackTrace() { delegate.printStackTrace(); } /** * {@inheritDoc} */ public void printStackTrace(PrintStream out) { delegate.printStackTrace(out); } /** * {@inheritDoc} */ public void printStackTrace(PrintWriter out) { delegate.printStackTrace(out); } /** * {@inheritDoc} */ public final void printPartialStackTrace(PrintWriter out) { super.printStackTrace(out); } }